Dynamic properties of III–V polytypes from density-functional theory

Abstract

The recently discovered hexagonal wurtzite phase of several III–V nanowires opens up strong opportunity to engineer optoelectronic and transport properties of III–V materials. Herein, we explore the dynamical and dielectric properties of cubic (3C) and wurtzite (2H) III–V compounds (AlP, AlAs, AlSb, GaP, GaAs, GaSb, InP, InAs, and InSb). For cubic III–V compounds, our calculated phonon frequencies agree well with neutron diffraction and Raman-scattering measurements. In the case of 2H III–V materials, our calculated phonon modes at the zone-center Γ point are in distinguished agreement with available Raman-spectroscopy measurements of wurtzite GaAs, InP, GaP, and InAs nanowires. Particularly, the “fingerprint” of the wurtzite phase, which is our predicted E2(high) phonon mode, at 261 cm−1(GaAs), 308 cm−1(InP), 358 cm−1(GaP), and 214 cm−1(InAs) matches perfectly the respective Raman values of 258 cm−1, 306.4 cm−1, 353 cm−1, and 213.7 cm−1 for GaAs, InP, GaP, and InAs. Moreover, the dynamic charges and high-frequency dielectric constants are predicted for III–V materials in both cubic (3C) and hexagonal (2H) crystal polytypes. It is found that the dielectric properties of InAs and InSb contrast markedly from those of other 2H III–V compounds. Furthermore, InAs and InSb evidence relative strong anisotropy in their dielectric constants and Born effective charges, whereas GaP evinces the higher Born effective charge anisotropy of 2H III–V compounds.